Field of the Invention
The present invention relates to an image formation apparatus and particularly to an image formation apparatus having a steering control function.
Description of the Related Art
An image formation apparatus includes around an image carrier a charging device, an exposure device, a developer, a transfer device, a cleaning device, a diselectrifying lamp, etc. The charging device charges the image carrier uniformly. Subsequently, the exposure device forms an electrostatic latent image on the image carrier. The developer develops the electrostatic latent image into a toner image. The transfer device transfers the toner image to a transported transferring material. The cleaning device removes residual toner on the image carrier. The diselectrifying lamp removes the electric charge of the image carrier. Image formation is performed by this series of steps.
In the image formation, an endless belt may be used as the image carrier or an intermediate transfer body. The endless belt (hereinafter also simply referred to as a “belt”) is tensioned and thus engaged on a plurality of rollers having at least a drive roller and a tensioning roller, and thus driven.
However, depending on the rollers' parallelism accompanying their arrangement, the rollers' precision as a cylinder, a difference between the opposite lateral edges of the belt in circumferential length, etc., there is a possibility that a phenomenon occurs in which the belt moves in a direction having a right angle relative to the direction of transportation (i.e., in the roller's axial direction), i.e., the belt meanders.
When the meandering phenomenon occurs, an image which is formed on the belt or an image which is transferred on the belt is offset and a satisfactory image cannot be obtained.
Accordingly, Japanese Laid-Open Patent Publication No. 6-56294 proposes, as a technique to control the meandering of the belt, an intermediate transfer unit which has a steering control function to control the belt's axial movement by moving one end of a roller that imparts tension to the belt to vary a distance which the belt's end travels.
Furthermore, Japanese Laid-Open Patent Publication No. 2009-31613 proposes a system in which, in an intermediate transfer unit having a steering control function, in order to remove residual toner on an intermediate transfer belt, a cleaning blade abuts against the intermediate transfer belt.